Present day integrated circuitry frequently requires precise and well-defined placing of material onto a target board. Usual respective materials include, for example, electrically conducting materials, such as metallic solders, as well as optically or electronically functionalized materials, such as luminescent substances or organic semiconductor solutions. Furthermore, relevant target boards may include substrates, integrated circuits, microchips, or packages for contacting and/or housing integrated circuits.
In the case of methods for placing material, it is essential to steadily reduce the volume of a single material portion as well as to reduce the distance between adjacent material portions (pitch), both for the purpose of progressive integration and an increased performance of a ready device.
If the spatial dimensions of the material portions are reduced to micrometers, a reliable and reproducible dense placing of material becomes increasingly difficult. On the one hand, it has to be guaranteed that a material portion is reliably placed at a predefined location with a sufficient precision, on the other hand, contact between two adjacent material portions is to be avoided. Not only if solder materials are used, physical contact between two adjacent portions may lead to coalescing and thus to a short circuit or malfunction of a device.
Precise methods make use of a template in the form of a transfer board that comprises recesses at the predefined respective positions for placing the material. Material portions are firstly deposited, often more or less serially by means of a dispenser, into these recesses. Subsequently, a correct filling of the recesses with material may be verified by inspection, and the material portions can then be placed onto the target board simultaneously in one step by a adequate positioning of the transfer board opposite the target board.
It is a conventional method to fill such a transfer board by means of a portioning device, a form of a dispenser, wherein such a portioning device comprises a number of nozzles and is scanned over the transfer board. While the portioning device travels over the transfer board, the nozzles are activated in such a way that material portions are ejected from the nozzles at the correct moment and are deposited in the corresponding recesses of the transfer board. The precision and reliability of such a procedure strongly depends on the precise drive and alignment of the portioning device with regard to the transfer board, and on the correct activation of the nozzles. Furthermore, scanning of the portioning device requires time, which usually renders such procedures slow and error-prone.